16th March 2006 VHF/UHF Knife-Edge Propagation                           LA2QAA

An Observation from Norway.

2m and 70cm knife-edge propagation is a well known phenomenon for those that live in mountainous areas.

Theoretically, from my QTH on Frei Island I shouldn't be able to work North America on a low earth orbit satellite due to the proximity of the extremely high mountains from N.N.W. of my antenna array to S.S.E. and since antipodal propagation is not as common this far north as it is nearer the equator the chances of satellite DX on a LEO are minimal ... though almost permanent auroral propagation makes life interesting via satellite ... remember, the signal traverses the ionosphere twice!.

That being said, by careful monitoring of a tracking program it is possible to find an AO-7 orbit where knife-edged propagation could be used to "sneak" around the edge of the mountains.

Bearing in mind an average 2 x 6 array has less than the more common 3dB half power point the "aiming" has to be fairly accurate. For the newcomer this means that only half of the uplink power will actually manage to scrape around the mountain ... (reflection and refraction also has to be taken into account, likewise eventual ground gain) ... therefore, there are a lot of variable to contend with ... not least the idiosyncracies of the ionosphere as well as the polarisation of the signal.

However, being an AO-7 aficiondo I've been trying for quite some time to defeat these mountains and get into the States while working AO-7.

Imagine my surprise therefore when after repeated CQ's I finally heard LA2QAA de K8DID.

I used to work the States daily on AO-13 but a relative LEO like AO-7 is a different matter from this particular QTH on Frei Island. JP33WB.

The moral of the story? ... don't give up, give it a try, you never know.

It was well worth the effort.

73 John.   <la2qaa@amsat.org>